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Gravseal – a cost effective surfacing solution for gravel roads

COLAS is working towards delivering more cost-effective surfacing solutions for low volume rural gravel roads with their semi priming rubber modified graded seal. A successful trial was constructed on 12 December 2018 on a 600m length of gravel road in the Bellingen Valley in NSW using Gravseal – a robust surfacing treatment based on the Otta seal concept. The semi priming binder was modified with rubber from used tyres and the graded aggregates were precoated to further improve the long-term performance of the surfacing. The trial section will be closely monitored so that Bellingen Council can assess the suitability of this treatment to overcome their gravel road maintenance back log.

Otta seals originate from Norway where the gravel from the glaciers were used with a soft bitumen to provide an all-weather surfacing. COLAS has further enhanced the performance of the Otta seal concept by modifying the binder with rubber from used vehicle tyres and precoating the aggregates. Gravseal is more cost effective than a new conventional 7/14mm double seal because the graded aggregate provides a stronger stone interlock which provides a more durable surfacing requiring less maintenance during its life.

Gravseal is also easier to construct because:

  • No priming of the base course is required
  • It can be constructed in a single operation and does not require two establishments
  • The binder is not sensitive to low ambient temperatures during construction
  • It can cope with uneven base courses because the graded aggregate acts as a better leveling course.

By sealing low trafficked gravel roads, the Councils will reduce their costs of grading and regravelling their rural unsurfaced road network. This will also eliminate the generation of dust which can result in higher fruit yields for the neighbouring farmers and provide all weather access to markets and their properties.

Spraying the semi priming rubber modified binder on the gravel base


Spreading the graded precoated aggregate on the semi priming binder


Finished surface after rolling

Published: Sat 08 December 2018